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2013 Chevrolet Suburban
Platform: GMT 400, 800, 900

02 Tahoe security flashing

Old April 15th, 2019, 9:49 AM
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Default 02 Tahoe security flashing

I had to rebuild my transmission on my 2002 Tahoe Flex Fuel 5.3L engine. I disconnected the battery cables before doing my tranny. I later found that i needed to replace leaky fuel lines and ultimately the plastic fuel lines over the gas tank which would not disconnect. I put it all back together to find the engine would not turn over only to find I forgot to plug in the neutral safety switch. The starter turned over fine after that but no fire. I dropped the tank again with the plastic fuel lines disconnected from the metal lines and found they were still dry. I cranked the engine to see if the fuel pump would spit fuel and got nothing. With the fuel relay out, I put a jumper across the gate ports and saw that the new pump and wiring worked fine. I interchanged 4 other identical relays and could not get the pump to spit when I cranked the starter. Then I noticed the Security light flashing on the dash. I know I need an active code reader to reset the security signal. My question is would the disconnected neutral safety switch during the starter cranking cause the anti theft security to engage? I don't want to get a mechanic to reset everything and then not understand what caution to take while I finish buttoning up the rest of my repairs.
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Old April 15th, 2019, 11:54 AM
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I am not quite sure the order of adjustments for the anti theft reset. I called a tech for a price on the reset and he said he would come out for $120. Another tech said he normally closes all the doors and puts the ignition key in the on position for 15 minutes and it successfully resets. 15 nor 20 minutes did not work for me but I still had the error codes registered. I disconnected the negative battery terminal to reset the error codes first, then I will try to reset the anti theft with the key in the on position with doors closed for 30 minutes. If it doesn't work I will have to pay the man to come out with his active OBDI. I just don't like when they say no guarantees and you still owe the fee.

Last edited by Makemyenginerun; April 15th, 2019 at 11:57 AM.
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Old April 15th, 2019, 2:19 PM
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Ok so I am noticing that the security light only flashes when the drivers door is open. With the door open and the key in the ignition not in run position the security light flashes. Once it is in the on position there is no security light flashing.When I crank over the starter there is no security light at all. Do I have a security anti theft problem???
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Old April 15th, 2019, 2:37 PM
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I have no error codes showing with OBDI scan tool. There are no communication errors with the PCM. I realize the ECM sends the neutral ground to the relay for 2 seconds and then the PCM engages continually after that but I am lost as to what to do at this point. Hey where are you guys LOL

Last edited by Makemyenginerun; April 15th, 2019 at 2:41 PM.
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Old April 19th, 2019, 10:44 AM
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I changed the computer hoping to get a favorable result but I still have the problem where terminal 85 and 86 on the fuel pump relay will not show voltage when the key is in the on position. The gate ports when using a jumper wire with the relay out makes the fuel pump work. Where does 85 or 86 receive the 12 volts from????
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Old April 19th, 2019, 11:28 AM
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I made an observation. With the negative battery cable disconnected and the fuel pump relay removed I do get 12 volts at both coil terminals 85 and 86 individually. As soon as I connect the negative battery cable the voltage at 85 and 86 of the fuel pump relay disappears with the key in on position. Even if I toggle from off to on I get nothing. Someone please help me with this. Walk me through.
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Old April 19th, 2019, 2:35 PM
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how are you getting 12v with the battery disconnected? even if its only the neg cable the circuit is still not there and you wont get any power
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Old April 19th, 2019, 3:32 PM
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Let me clarify that. Lol I made that confusing. I should have said I disconnected the negative cable from the battery. Then I put the positive voltage tester cable into relay terminal 85 then 86 with the negative voltage tester cable on the battery lead. There I found 12 volts in both 85 and 86 while the key is in on position. When I connect the negative battery cable to the battery the voltage at terminal 85 and 86 disappears.

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Old April 20th, 2019, 6:41 AM
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Originally Posted by Makemyenginerun View Post
..... I realize the ECM sends the neutral ground to the relay for 2 seconds and then the PCM engages continually after that but I am lost as to what to do at this point. Hey where are you guys LOL
I believe you may have this backwards. The PCM sends the 12V to the pump relay terminal 85, terminal 86 is ground. You should see 12V on terminal 85 when you turn the key on or start. Check for continuity on terminal 86 to ground. ( I think have the terminal numbers correct)
I'd be looking for a ground wire that didn't get bolted down (or broken off) when you repaired the tranny.
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Old April 20th, 2019, 8:36 AM
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86 has a positive 12.4 ohms ground with the relay out and the key in the on position. 85 does not ground. The cable to the battery ground was connected for this test.
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